Tropical Fish Hobbyist - October 2010

Age and Size In clownfishes, sex is determined by rank and size is determined by sex. An adult fish will be one of three different sizes. In the wild a small group of juvenile, sexually undifferentiated clowns will occupy an anemone. The dominant fish will become a female and grow to maximal size. The second-ranking fish will become a functional male and grow to the second size. All the rest remain quite small, the third size. If the female is lost, the male will become a female and grow to full size, and one of the small fish will become a male and grow to medium size. It is quite possible for one of the sexually undifferentiated never to become a male or female and to live out its life at the smallest size. Thus a small clownfish that is wild caught could be a juvenile just establishing itself on the reef, or it could be a geriatric specimen nearing the end of its life.

…But Not for All Not all nano aquariums can realistically support a clownfish or damselfish for the long term. Don’t assume that just because one of these fishes can fit in a very small nano system that it will be healthy and happy there over the course of its life. Pomacentrids can live for well over a decade in captivity, and they deserve the best care we can provide over the course of that long lifespan. So we have to be realistic about the volume of water we attempt to keep them in. Would a 20- to 30-gallon system suffice for a small to medium-sized pomacentrid, provided it is well maintained and appropriately stocked? Almost certainly. When you move into the 10- to 12-gallon nano range, you’re definitely entering borderline territory, although it could be done with meticulous maintenance and attention to water parameters. But a 5-gallon or smaller system? Consider these out of the question for even the smallest clownfish or damsel.

smaller clownfish species such as the ocellaris and percula clowns, can be considered reasonable candidates for these smaller systems.

to tell you where their fishes come from (remember, fishes collected from the Philippines or Indonesia should be considered suspect) and whether or not they were collected in a sustainable manner.

• As mentioned earlier, purchase captive-bred fishes whenever possible. There’s obviously no risk that those specimens have been exposed to cyanide.

• Be willing to pay a few extra dollars for net-collected fishes. An inexpensive fish is no bargain if it dies shortly after purchase.

• If it is available in your area, purchase livestock that has been certified by the Marine Aquarium Council (MAC). MAC certification is your insurance that a fish has been collected, handled, and shipped in a sustainable fashion.

Choosing a Tank for Pomacentrids Is No Big Deal

Having limited space in your home to accommodate an aquarium is not necessarily a limitation on keeping clownfishes and damselfishes. Many are well suited to life in a modest-sized home aquarium in the range of 20 to 40 gallons. Even tanks that would be considered grossly undersized for many other reef fishes can be suitable housing for certain pomacentrid species.

Nice for Some Nanos...

With the burgeoning popularity of nano aquariums—defined for our purposes as systems of 30 gallons or smaller—the demand has risen for marine fishes that can adapt to life in such confined quarters. Many pomacentrids, especially certain

Some collectors use cyanide to catch damsels and other fish, a practice that threatens the survival of coral reefs. Avoid purchasing cyanide-collected fish.

Nano Negatives

Because so many pomacentrids are good candidates for smaller aquariums, it behooves us to examine some of the drawbacks inherent in these systems. These challenges shouldn’t necessarily be viewed as deal breakers for the aspiring clownfish or damselfish keeper, but understanding that they exist is the first step toward overcoming them.

David Nielsam

Instability A smaller volume of water is far less stable than a larger volume in terms of its temperature, pH, specific gravity, etc. Changes for the worse occur much more rapidly in a nano tank than they do in a larger system. If the ambient air temperature shifts markedly upward or downward, the water temperature in a smaller volume of water will change much more rapidly than it will in a larger volume of water. Compare the respective cooling rates of a cup of coffee and a pot of hot water and you’ll get the general idea.